1. Field of the Invention
The present invention relates to a method and apparatus for a path trace check.
In a digital synchronization network, multiplex transmission data multiplexed by multiplex conversion equipment is transferred over a fiber transmission path connecting a plurality of nodes in a ring. In each of the nodes, required data is dropped from the multiplex transmission data or the required data is added to the multiplex transmission data.
The transmission data is multiplexed by for example the STS-1, VT1.5, or other prescribed frame format and, at the same time, given overhead data for transfer control or transfer management for each frame format data. Various types of transfer control information and transfer management information are contained in this overhead data. Among them, there is path trace data. The present invention relates to a path trace check using this path trace data.
Note that this path trace data is generally transferred using the J1 byte used in for example STS-1 multiplex transmission data or the J2 byte used in the VT1.5 multiplex transmission data. These path trace data (J1, J2, etc.) are for indicating through which path in the network the multiplex transmission data containing the related path trace data was transmitted. By analyzing this path trace data at the receiver side, the channel quality such as the error rate of the related path, can be determined.
2. Description of the Related Art
As will be explained in detail later by using the drawings, a path trace check apparatus of sender side (PT.sub.s) and a path trace check apparatus of receiver side (PT.sub.r) are formed in a multiplex conversion apparatus (MUX) in the related art. Each of these apparatuses is equipped internally with a microcomputer (.mu.-COM) explained in detail later. The path trace check apparatus of the receiver side (PT.sub.r) is further equipped with a synchronizing unit explained later. Such a path trace check apparatus suffers from the following problems.
First, when viewing the path trace check apparatus (PT.sub.s) of the sender side PTs, there is a first problem that the microcomputer (.mu.-COM) directly handles the transmission of frame bits so the load applied to the microcomputer becomes large.
Further, when viewing the path trace check apparatus PT of the receiver side (PT.sub.r), there is a second problem that the microcomputer (.mu.-COM) directly handles the processing for extraction of the path trace data so the load applied to the microcomputer becomes large in the same way as the above case.
Further, the path trace check apparatus PT of the receiver side (PT.sub.r) of the related art is configured so that the synchronizing unit extracts the path trace data. Namely, it is based on a frame synchronization system. For this reason, the following third, fourth, and fifth problems arise.
Usually, a considerably long time is required for establishing synchronization in the case of frame synchronization. For this reason, a considerably long time is taken until the microcomputer extracts the path trace data and finishes deciding on the state of the channels. This is the third problem.
In this case, the cycle of appearance of the overhead OH (path overhead) is for example a slow one of 4 kHz. A considerably long time is therefore required until all path trace data is extracted. This is the fourth problem.
Further, networks NW are comprised of a large number of nodes and the number of the nodes will unquestionably increase in the future. If the number of nodes increases, with the frame synchronization method, it will be necessary to reset the timing due to the addition of the frame bits to be preassigned to each of the nodes. Namely, it will not be easy to cope with an increase of the number of nodes. This is the fifth problem.